1. Field of the Invention
The present invention relates to a permanent magnet motor, and more particularly to a permanent magnet motor with lower cogging torque.
2. Description of the Related Art
Cogging of a motor affects performance and also produces vibration and noise, causing restriction and inconvenience in use of the motor. Therefore, the conventional art is all devoted to the research and development of reduction on a cogging torque of a motor, and the prior art intending to reduce cogging by technical means such as a shape, a size, a pole pitch and a magnetization mode of a magnet, an opening angle of magnets, a depth of a boot, a combination of the number of slots/poles, and an auxiliary slot is disclosed.
Specifically, the prior art shown in FIG. 1 discloses a built-in construction that achieves the efficacy of reducing cogging by changing an opening angle of a pair of magnets (2) of a rotor (1), in which the pair of magnets (2) is buried in a V shape in the rotor (1). Furthermore, as shown in FIG. 2, a construction of a hole (4) is further disposed in a magnetic island (3) of each pole, so that the magnetic field lines is restricted by the hole (4) and thus the magnetic field lines are more concentrated to have more efficient linkage with a stator winding, thereby achieving the efficacy of reducing a cogging torque.
Although such conventional art discloses hole constructions to change flux distribution of a rotor core, the prior art lacks optimized detailed technical content such as the shape, the number, the size and the position of the holes for the efficacy of reducing the cogging torque. The deficiency of the prior art needs to be overcome.